I just leveled my Enhineer to 450, whats next?   I have a 450 Herbalist, Jewel Crafter that can either make a potion that can randomly learn a new recipe or (JC) can do quests to gain recipes.  Although my enchanter isnt but 407 i can see that the vendor next to the trainer in dalaran also provides recipes that can be bought by the same system that the JC can.... So if these other professions have a way to gain more recipes, isnt there something an engineer can do?  i am hoping that there is and i just havent figured it out yet. 

So can anyone tell me a way to gain more recipes for my goblin engineer or my gnome engineer when he reaches the 450 mark too?

I've never made an engineer, but if you want an addon that tells you what recipes you are missing, and where/how to find them, try Ackis Recipe List, which works with every tradeskill, including the secondaries.